The present invention relates to a flow type particle image analytical method and apparatus for generating an image of particles in a sample, which form a suspended flow of the sample, by irradiating light to the formed sample flow and automatically classifying the particles in the sample by analyzing the generated particle image, and particularly to a flow type particle image analytical method and apparatus suited to classify and display the particle image based on configurational features such as configuration, size or color of the particle image according to biological kinds of particles such as cells in blood or urine.
To conventionally classify and analyze particles such as cells in blood or cells existing in urine, a sample is prepared on a glass slide sheet and observed with a microscope. In the case of urine, the particle concentration in the urine is thin, so that a measuring sample is centrifugalized and concentrated by a centrifuge beforehand and then observed. In an apparatus for automating these observation and examination work, a sample of blood or other material is coated on a glass slide and set in a microscope, and the microscope stage is automatically scanned and stopped at a position where particles exist. A still image of particles then is picked up and particles in the sample are classified by using a characteristic extraction and pattern recognition method by the image processing art.
However, in the aforementioned method, it takes a lot of time to prepare a sample and an operation for finding a particle by moving the microscope stage mechanically and moving the particle into a suitable image fetching area is required. As a result, problems arise in that the analysis requires a lot of time and the mechanism is complicated.
To realize high precise examination and labor saving, there is a flow type particle image analytical apparatus using a flow cell for using a sheath solution which has a cleaning solution as an outer layer and controlling the sample solution to an extremely flat flow which is disclosed in, for example, U.S. Pat. No. 4,338,024, Japanese Patent Application Laid-Open 63-94156, and Japanese Patent Application Laid-Open 4-72544.
In the flow type particle image analytical apparatus, a sample moving in a flow cell is imaged, for example, by a video camera and the particles in the sample are classified and counted by processing the picked-up still image.
As a flow type particle image analytical apparatus for imaging particles in a sample by changing the magnification, a particle analytical apparatus is described in Japanese Patent Application Laid-Open 3-105235 and Japanese Patent Application Laid-Open 4-309841.
The flow type particle analytical apparatus described in Japanese Patent Application Laid-Open 3-105235 and Japanese Patent Application Laid-Open 4-309841 mentioned above comprises a stroboscope continuously emitting light having a short emission time, a stop for adjusting the quantity of the stroboscopic light, a diffusion plate for eliminating variations in the quantity of stroboscopic light, a condenser lens for focusing the stroboscopic light, a flow cell which is arranged in the position where the stroboscopic light passes and lets a sample flow flat by surrounding the sample by a sheath solution, an object lens for forming an image of a particle irradiated by the stroboscopic light, a high-powered projection lens, a low-powered projection lens, a TV camera for picking up an image, a means for moving the diffusion plate, a means for changing the aperture stop, and a switching means for switching the high-powered projection lens and low-powered projection lens.
A method for classifying a particle image formed by the aforementioned flow type particle image analytical apparatus by the particle size and displaying it on a CRT screen and classifying particles by an operator is proposed in U.S. Pat. No. 4,612,614.
However, there is the following problem imposed in the flow type particle image analytical apparatus described in U.S. Pat. No. 4,612,614 mentioned above.
Namely, it is premised in the flow type particle image analytical apparatus that the particle classification work is reviewed by an operator by watching an image on the CRT and an extremely large image memory is necessary so as to analyze all particles in a sample. Particularly in a sample having a large particle concentration, all particles cannot be stored in a limited image memory and furthermore it requires a lot of time for an operator to proceed with the classification work by watching images. When the image memory is not sufficient, the number of particles to be reviewed decreases and it is difficult to expect a reproducible classification result.